Typically, during electrosurgery, an electrosurgical generator provides a high frequency or radio frequency signal to a hand-held surgical electrode having a thin knife-like tip which is applied to a patient. The patient is grounded to the generator via a patient ground plate. The relatively small area of contact by the electrode with the patient provides an intense current in a highly localized area, producing a cutting action. This current then passes through the patient's body to the patient ground plate wherein the area of contact is large enough that no burning effect occurs at this location.
To produce this cutting action, the generator is activated to produce a continuous signal, typically a sine wave signal. The same instrument may also be applied to the wound after cutting in order to produce coagulation. This coagulation is produced by a pulsing signal from the generator. Switching means are thus needed to enable the operator to switch between the two types of electrical energy produced by the generator.
Although a number of arrangements have been devised for selectively activating the electrical energy, the most satisfactory of these arrangements is a multiple wire cable conductor extending from the generator to the hand-held electrode. One conductor is normally connected to the electrode to carry the therapeutic current (cutting or coagulating) and two other conductors are selectively connectable to the therapeutic current conductor through switches to complete circuits back to the activating means for causing the generator to produce the desired mode of current.
For use during endoscopic surgery, surgical instruments, including electrosurgical instruments, typically are provided with elongated barrel members that may be directed through an appropriately sized trocar tube. In these types of instruments, it is well known in the art to provide suction and irrigation capabilities in addition to the electrosurgical therapeutic current capabilities so that several functions may be provided through one trocar tube. Also, in these type of instruments, because the electrode tip is located at the end of an elongated device, it can be difficult to accurately control. Therefore, a pistol grip handle is often used to provide more accurate control.
One such instrument is disclosed in U.S. Pat. No. 5,273,524 to Fox et al. (Fox). The Fox patent discloses an electrosurgical instrument having an elongated barrel member attached to a handle member. Therapeutic current (cutting or coagulating) is provided to an electrode which is selectively extended from a sheath at the distal end of the barrel member. Push buttons located on the back of the handle member selectively connect either suction or irrigation to the barrel member and the push buttons control this selection by pinching the respective suction or irrigation tube when the button is in the released position and releasing the tube as the button is depressed.
U.S. Pat. No. 5,295,956, to Bales et al. (Bales) discloses an endoscopic instrument which provides cutting or coagulating current to an electrode which is located axially within an elongated cannula and protrudes from the distal end of the cannula. One of a variety of electrodes is inserted into the instrument through the back of the handle. Current to the electrode is activated by thumb switches that are located on the back of the handle. Two triggers are provided on the front side of the handle and are actuated by the user's fingers for selectively providing suction or irrigation to the cannula. Similarly to the buttons in the Fox patent, in the released position, each trigger pinches a tube that supplies either suction or irrigation to the cannula and, in the depressed position, each trigger releases its respective tube, allowing either suction or irrigation to reach the cannula. The Bales patent also discloses a safety switch which disconnects the electrical connection between the current supply cable and the electrode when either of the switches is depressed, i.e., when suction or irrigation is being used, so as to prevent burns and shocks to the patient. Variable suction strength is provided to the end port of the cannula by a sleeve which slidingly engages the cannula and is moved longitudinally to selectively expose lateral holes at the proximal end of the cannula.
U.S. Pat. No. 4,936,842 to D'Amelio et al. (D'Amelio), discloses an electrosurgical instrument wherein a bipolar electrosurgical probe is rotatably connected to a handle portion. Rotation of the probe with respect to the handle portion allows the surgeon to position the active portion of the probe as needed.
While the instruments disclosed in the prior art provide useful features, these features have not been implemented in the most effective, safe, reliable, and efficient manner.